Iron(III) complexes of 2-(1H-benzo[d]imidazol-2-yl)phenol and acetate or nitrate as catalysts for epoxidation of olefins with hydrogen peroxide

Abstract Cheap and environmentally friendly Fe(III) catalysts [Fe(L) 2 (CH 3 COO)] ( 1 ) and [Fe(L) 2 (NO 3 )]·2CH 3 OH ( 2 ) where HL = 2-(1H-benzo[d]imidazol-2-yl)phenol for epoxidation of olefins have been developed. The catalysts have been characterized by elemental analyses, IR, UV–Vis spectroscopy and by X-ray crystallography. The X-ray structures reveal mononuclear compounds having a bidentate acetate or nitrate in 1 and 2 , respectively. Catalytic epoxidations of styrene and cyclohexene have been carried out homogeneously by using 30% aqueous hydrogen peroxide in acetonitrile in the presence of catalytic amounts of 1 or 2 . Yields of the respective epoxides were fair ( 1 ) to good ( 2 ) and selectivities were good in all cases although 2 produced two to three times the yield, depending on the substrate, than 1 and higher selectivity as well. A hypothesis for these differences in catalytic efficacy between 1 and 2 that is consistent with mechanistic details of related enzymatic and biomimetic model systems is proposed. Herein we report [Fe(L) 2 (NO 3 )]·2CH 3 OH ( 2 ) as the first structurally characterized non-heme iron epoxidation catalyst with a bidentate nitrate ligand.